Process and apparatus for taking a representative milk sample

ABSTRACT

A process and apparatus are disclosed for taking a representative milk sample during the delivery of a milk charge from one container to another. With respect to the errors encountered in operating peristaltic pumps with different speeds of revolution, the invention predetermines a corrected pumping characteristic as a function of an acceptance characteristic and correspondingly controls the taking of samples.

BACKGROUND OF THE INVENTION

The invention relates to a process for taking a representative milksample and to an apparatus, particularly for performing the process.

A process and an apparatus of the aforementioned type are e.g. knownfrom DE 35 02 858 A1. In the known apparatus a milk sample is activelypumped by means of a peristaltic pump from a delivery line into a samplebottle for example during the transfer of a milk charge from onecontainer to another. The peristaltic pump is controlled in such a waythat, in accordance with a previously inputted desired quantity for themilk charge, the sample bottle for the latter is filled in accordancewith a desired volume.

In order to obtain a reproducible desired volume, it is necessary tohave information on the acceptance capacity of the milk collectingcontainer which may be a truck or trucks. For this purpose hitherto oneparameter has been fixedly predetermined in a preprogrammed manner, sothat the sample bottle for receiving the milk sample has been constantlyfilled to a greater or lesser extent.

As the aim is to take a continuous representative milk sample of theentire milk charge, the milk sample removal process must be controllableas a function of the total milk charge volume. The term a representativemilk sample is understood to mean that only a maximum volume isavailable in the sample bottle intended for the milk sample and on theother hand that, if possible, the milk sample should have a roughlyconstant volume, independently of whether a lower volume milk charge ora very large milk charge is delivered. The sought constant volume forthe milk sample results from the fact that certain minimum milk samplequantities are required for investigations and tests.

Another objective of the representative milk sample is to draw thelatter over the entire delivery cycle of the corresponding milk charge.However, since, as a function of the volume, the milk charges are suckedwith different deliveries, e.g. from a tank and pumped into the milkcollecting truck or tanker, so that different delivery times occur,account must also be taken of this aspect within the scope of arepresentative milk sample.

In addition, when using a peristaltic pump for taking a representativemilk sample, a further problem occurs in that the delivered volume isnot in a linear relationship with the speed of revolution of theperistaltic pump. If it is assumed, for example, that a peristaltic pumpdelivers a volume z1 after y revolutions in the case of a speed ofrevolution of x1, then normally the volume z2 delivered at a higherspeed x2 after y revolutions will be smaller than z1. This is attributedto the fact that the hose or tube used does not have sufficient time,particularly if high speeds are used, to reassume its original hose ortube diameter, in order to achieve its normal capacity.

Thus, with a larger volume of a milk charge to be delivered, itsdelivery takes longer, the milk sample being taken in a continuousmanner and as a result of the lower speed of revolution of theperistaltic pump a higher than desired milk sample volume is taken.

Further problems in the delivery of a milk charge and taking arepresentative milk sample are that the delivery or pumping capacitycharacteristic may be influenced by factors which lead to a divergencecompared with the desired or nominal delivery. Reference is e.g. made todifferent or too narrow cross-sections in the delivery line or in thecollecting area on the milk tank. The pumping capacity can also beinfluenced by filter fluff in the screen of the collecting line andpossibly as a result of the drive this does not coincide with thenominal capacity or delivery. The way in which the milk is collectedalso affects the pumping capacity, if e.g. with a relatively large airadmixture, particularly at the end of the delivery operation, milk issucked from the tank or tanks, which are subject to a downward suctionaction, and which can be difficult to empty due to an inadequateinstallation of the tank. Problems can also occur due to incorrecthandling by the driver during the delivery process.

Such fault and error sources consequently influence the delivery anddelivery time for transferring a milk charge from one tank into another.

SUMMARY OF THE INVENTION

An object of the invention is to so improve a process and an apparatusof the aforementioned type, that the aforementioned disadvantages areminimized and with the aid of the control means for the pump,specifically a peristaltic pump, it is possible to take a representativemilk sample, even for different milk charge volumes.

The invention takes account of an acceptance or collectingcharacteristic for the feed pump used for delivering the milk charge orfor pumping round or recycling, as well as a pumping characteristic forthe peristaltic pump. As a result of this pumping characteristicquantity losses at higher speeds of revolution can be compensated by acorresponding increase in the number of revolutions n. On controllingthe sampling means having the peristaltic pump by such means there is acorrection to the speed of revolution of the peristaltic pump inaccordance with the stored pump characteristic.

In addition, according to the invention, the delivery for the recyclingof a milk charge is controlled as a function of an acceptance orcollecting characteristic. In order to ensure an effective recycling ordelivery of a corresponding milk charge, modern milk collecting trucksoperate as a function of the volume of the milk charge to be recycledwith different delivery rates. Thus, the apparatus for delivering themilk charge in the case of a milk collecting truck or tanker up to thecollection of 40 liters (1) can be operated at an average delivery of230 1/min, whereas e.g. 100 1 can be recycled with a delivery of 2601/min and delivery up to e.g. 320 1/min and higher are possible.

Thus, the delivery influences the control of the peristaltic pump,because for this there must not only be a time, but also a volumedependence. Thus, the plotting of the collecting characteristic isempirically determined by different quantities and is also stored. Thisstorage appropriately takes place in the form of supporting values(interpolation nodes) for different quantities, e.g. at a milk charge upto 10 1 with a delivery of 150 1/min or at a milk charge up to 40 1 witha delivery of 230 1/min. As a function of the number of such supportingvalues, it is possible to very accurately simulate the collectingcharacteristic.

Appropriately the maximum possible sample bottle volume, into which ispassed the representative milk sample is defined with a degree ofoverfilling of e.g. 120%. In other words the sample bottle is normallyfilled to a significant extent, e.g. up to 70% of its actual volume inthe case of coincidence between the desired and actual volumes of themilk charge to be delivered. With an increased actual milk chargevolume, the possibility then exists to take a further milk sample forthe milk charge volume exceeding the desired volume up to apredeterminable and programmable degree of overfilling, so thatreference can genuinely be made to a representative milk sample.

The taking of the milk sample is appropriately controlled via sensors,which determine the start and finish of milk charge delivery.

To ensure an effective pumping round or recycling of the milk charge,advantageously working takes places with stepped deliveries. In caseswhere the predetermined degree of overfilling of the sample bottle isnot sufficient and further milk charge delivery takes place, the milksample taken can no longer be looked upon as representative, so that anerror code is established.

In order to be able to determine and eliminate practice-related errorsources, e.g. different diameters for the delivery hoses, etc., from aprocess and apparatus standpoint, the desired delivery time ispredetermined and compared with the actual delivery time. If the desireddelivery time is exceeded, an error code is outputted, taking account ofthe actual milk charge volume.

The apparatus according to the invention comprises at least one dataacquisition unit, which is connected to a control mechanism. Thefunction of the latter is to control the sampling means and inparticular the peristaltic pump as a function of the pumping of thepumping and collecting characteristic and while taking account of thedetermined desired and actual data.

The storage of both characteristics appropriately takes place in thecontrol mechanism, but for special purposes advantages also result froma decentral storage in the sampling means or the data detection unit.

With the aid of the inventive process and the corresponding apparatus itis consequently possible to obtain a representative milk sample, makingit possible not only to eliminate volume losses due to the hithertoknown control means for peristaltic pumps, but also the error factorswhich occur in practice. In addition, the process and apparatus alsohave the flexibility for defining and storing degrees of overfilling forthe sample bottle, so that apart from extreme divergences, it is alsopossible to determine with a representative milk sample larger milkcharge volumes, which significantly exceed the desired values.

The invention is described in greater detail hereinafter relative to ablock circuit diagram and two characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1 is a block circuit diagram of an apparatus according to theinvention.

FIG. 2 is a graph showing an acceptance characteristic A with arepresentation of the delivery as a function of the milk chargequantity.

FIG. 3 is a graph showing a pumping characteristic P as a function ofthe number of revolutions n compared with the speed r.p.m.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1 diagrammatically shows a block circuit diagram of an apparatusfor taking a representative milk sample during the delivery of a milkcharge from one tank to another. The milk charge to be delivered iscontained in a tank 1, which e.g. has on its outside a code carrier 10for identifying the supplier. By means of a reader 2 the said codecarrier is read and the data inputted into a data acquisition unit 3.

The data acquisition unit 3 contains a stationary or mobile data carrier4, which stores the desired data for the supplier, e.g. the expectedmilk quantity. The desired milk charge value can be an automaticallydetermined value of a preceding number of milk charges. If the operatorestablishes that the desired value differs significantly from the actualvalue of the milk charge, it is possible to manually give a modifieddesired value via the data acquisition unit 3. The data stored orinputted into the data acquisition unit 3 is now available to a controlmechanism 5, in order to control the sampling means for a representativemilk sample.

The sampling means 6 essentially has a peristaltic pump, which pumpsfrom a line 11 the representative milk sample into a sample bottle 7. Inaddition, the pumping characteristic P can be stored in the samplingmeans.

The delivery of the milk charge from tank 1 to a collecting tank, suchas e.g. that of a milk collecting truck or tanker, takes place in thedirection of the arrow by a delivery or feed line 9, to which isconnected a feed pump. The actual milk charge delivery, i.e, the startand finish of the delivery is monitored by means of sensor 8, which isat least connected to the sample means 6.

On e.g. using as a basis a 50 liter milk charge, then the apparatusfunctions as follows. In a starting phase the feed pump for recyclingthe milk charge is operated for the first 20 1 with a delivery of 1501/min. This corresponds to a feed or delivery time of 8 s (seconds)(FIG. 2.) The peristaltic pump in the sampling means 6 is started at thebeginning of the delivery of the milk charge by means of sensor 8 andoperates with the 8 s setting corresponding to the corrected pumpingcharacteristic P (FIG. 3).

Following this first 8 second time interval the control mechanism willtransfer the next delivery corresponding to the acceptance or collectingcharacteristic, e.g. 230 1/min, so as to recycle the next 20 1therewith. A computer unit, which can e.g. be located in the dataacquisition unit 3, correspondingly calculates a recycling time of onthis occasion 5.22 s. Simultaneously for said second interval the speedof revolution of the peristaltic pump is increased and operated for atime interval of 5.22 seconds.

For the remaining 10 1 of the milk charge to be recycled, the deliveryis increased to 280 1/min after reaching 40 1. Correspondingly, in athird interval the feed pump and the peristaltic pump operate purelymathematically for 2.11 s.

However, the effective stopping of the peristaltic pump is controlledvia sensor 8, as soon as no further milk is detected or it detects thedesired value for the degree of overfilling of the sample bottle.

FIG. 2 shows an acceptance characteristic A, where the milk chargequantity to be delivered is plotted on the abscissa and the delivery inl/min on the ordinate. In the example, this acceptance characteristic Ahas a significant gradient and then approaches an asymptotic path forquantities of e.g. above 80 l.

The following values are given as supporting values for this acceptancecharacteristic: for 20 1 a delivery of 150 1/min; for 40 1 a delivery of230 1/min; for 60 1 approximately 280 1/min; and for 80 1 approximately300 1/min. Acceptance characteristics of this type are generally plottedempirically and in a construction-dependent manner.

FIG. 3 shows a possible empirical pumping characteristic path. Thepumping characteristic P gives the number of revolutions n (ordinate)compared with the speed r.p.m. (abscissa) for the same, pumped milksample volume. The path of the pumping characteristic P is initiallyalmost linear up to 200 r.p.m. and then assumes a roughly exponentiallyrising character.

With respect to the degree of filling and overfilling the apparatus canbe programmed e.g. via the data acquisition unit in such a way that ondelivering a milk charge in which the actual data correspond to thedesired data, the degree of filling is defined as 100%, the effectivesample bottle volume only being e.g. 75% used.

The sample bottle overfilling percentage can consequently be inputtedand is normally set at 20%. It is correspondingly possible to fill thesample bottle with milk sample up to a degree of filling of 120% and inthis range there are also standard variations of the milk charge volume.If, in spite of this, the milk charge delivery is to be continued andthe degree of filling of the sample bottle is already 120%, then thesampling operation is stopped by the control mechanism and an error codefor this milk sample is stored. The milk charge delivery obviouslycontinues up to the end.

If there is a downward milk charge volume variation, so that the actualquantity is smaller than the desired quantity, then the aforementionedproblem with regards to the degree of filling of the sample bottle doesnot exist. Obviously also here an "underfilling" could be looked upon asnon-representative and an error report could be stored. However, as arule the underfilling is considered to be acceptable and thereforerepresentative for the delivered milk charge.

Thus, at the end of the delivery of the particular milk charge, theinvention makes it possible to store all the values of the correspondingmilk charge and the representative milk sample taken. The possibility ofa printout can also be provided. In addition to the standard data suchas the supplier number, date time, temperature, pH-value and volume, thesample bottle degree of filling obtained is also stored and recorded.

Thus, the invention makes it possible to largely exclude error sourcesof a conventional nature, so that it is possible to take representativemilk sample from a corresponding milk charge.

What we claim is:
 1. A process for taking a representative milk sampleduring delivery of a milk charge from a tank into a collecting tank by afeed pump, comprising:inputting supplier data and data for the milkcharge into a data acquisition unit; supplying the inputted data to ameans for controlling a sampling means; taking the representative milksample using said sampling means and a peristaltic pump; storingdelivery capacity of the feed pump as an acceptance characteristic (A)of the milk charge to be accepted; storing number of revolutions (n) ofthe peristaltic pump as a pumping characteristic (P) of the rotaryvelocity of the peristaltic pump for a volume (z) of the milk sample tobe delivered; wherein the delivery capacity of the feed pump during theacceptance of the milk charge is defined by the control means as afunction of the volume of the milk charge to be accepted in view of theacceptance characteristic (A); and wherein the number of revolutions ofthe peristaltic pump is controlled by the control means as a function ofthe rotary velocity in view of the pumping characteristic (P), and therotary velocity of the peristaltic pump is defined as a function of thedelivery capacity selected with respect to the acceptance characteristic(A).
 2. A process according to claim 1, wherein delivery parameters ofthe milk charge takes place with stepped modifications and in particularan increase of the delivery capacity as a function of desired data andmeasured actual data of the milk charge.
 3. A process according to claim1, wherein desired and actual data are compared at the milk chargedelivery and defined volume values for the representative milk samplecan be determined at which, if exceeded, an error identification takesplace.
 4. A process according to claim 1, wherein the values of thedegree of filling, and the degree of overfilling of a sample bottle arestored in relation to the effective volume of said bottle.
 5. A processaccording to claim 1, wherein the expected desired volume of the milkcharge to be delivered is manually inputted into the data acquisitionunit.
 6. A process according to claim 1, wherein the delivery capacityfor milk charge delivery is controlled as a function of the acceptancecharacteristic and the stored values.
 7. A process according to claim 1,wherein means for sensing detect the start, and finish of milk chargedelivery for controlling milk sample removal.
 8. A process according toclaim 1, wherein the taking of the milk sample is carried out intime-controlled manner for the duration of the delivery of the milkcharge.
 9. A process according to claim 1, wherein the desired deliverycapacity for the milk charge delivery is taken into account when settingthe feed time for the milk charge in accordance with the acceptancecharacteristic.
 10. A process according to claim 1, wherein in each casea substantially constant volume of the milk sample is taken at differentmilk charge quantities.
 11. A process according to claim 1, wherein thedegree of filling of the sample bottle for the representative milksample to be taken takes place as a function of the actual milk deliveryquantity.
 12. A process according to claim 1, wherein the deliverycapacity for milk charge delivery is controlled as a function of theacceptance characteristic.
 13. A process according to claim 1, whereinthe delivery capacity for milk charge delivery is controlled as afunction of the stored values.